Donkey Kong GB is a platform video game where you play as Mario and try to rescue Pauline from Donkey Kong. Donkey Kong Jr. also appears in the game to hinder Mario's progress on certain levels.
You control Mario, and the big ape Donkey Kong has kidnapped Mario's friend Pauline and taken her to a construction site. Like in the original Donkey Kong game, Mario follows Donkey Kong to the top of the construction site and makes him fall by removing the rivets supporting the platforms. This reunites Mario and Pauline, but Donkey Kong recovers unexpectedly, takes Pauline, and escapes to the Big-City. Mario chases after them.
Donkey Kong GB involves a chase through different locations. Mario defeats Donkey Kong at the end of each world, but Donkey Kong keeps getting up and taking Pauline to the next location. Donkey Kong is helped by his friends and his son, Donkey Kong Jr., who try to hinder Mario's progress. Eventually, Donkey Kong escapes to the Tower in Rocky-Valley, where he and Mario have a final confrontation. After defeating Donkey Kong, Mario and Pauline are reunited, and they all make amends with each other.
Construction Site: Mario's goal is to reach Donkey Kong at the top of the 25m, 50m, 75m, and 100m stages. Mario faces enemies like Fireballs and platforms with gaps to jump across.
Big-City: Mario needs to unlock doors with keys in this world. It serves as an introduction to the game's basic items and moves, such as handstands, roads, and ladders. There are two boss fights with Donkey Kong.
Forest: The Forest introduces vertical ropes to climb and water to swim in. Mario encounters switches that can make roads appear or disappear. There are enemies called Snapjaws that climb ropes, which can be defeated with fruit. These stages reference Donkey Kong Jr.
Ship: Ship stages expand on previously introduced game objects and add new puzzles. Mario must use Handstand Double Jumps, Wire Spins, and Walking Blocks to progress.
Jungle: The Jungle expands on the Forest's level types. Mario must navigate complex vertical ropes and is helped by ally creatures like Monkikki and Jumpers. Enemies like Dorakyū hinder Mario's progress.
Desert: The Desert introduces Super Hammers to break through walls. Puzzles become more complex, and one stage requires Mario to carry a Key up several stories using ladders, roads, and Jump Stands.
Airplane: Airplane levels feature winds that blow Mario sideways. Mario encounters elevators, conveyor belts, and cannons. There are multiple locked doors, and the player must choose the correct one.
Iceberg: The Iceberg features slippery surfaces. Mario jumps across sinking rocks and uses icicles as platforms.
Rocky-Valley: Rocky-Valley has the most challenging puzzle stages, requiring strategic thinking and precise knowledge of the game's physics.
Tower: The Tower is the final stage. Each level is a boss fight with Donkey Kong or Donkey Kong Jr. Mario must avoid obstacles like Poison Mushrooms and sand blocks. After defeating Donkey Kong in stage 9-8, Mario fights him again in his giant form in stage 9-9.
Donkey Kong GB starts with four simple levels where Mario climbs to reach Pauline. After that, Donkey Kong escapes to the city and beyond, and the game introduces puzzle levels and more showdowns with Donkey Kong.
Each world has puzzle levels where Mario must complete tasks within a time limit. These tasks involve building platforms, using switches, jumping on moving platforms, and avoiding enemies. Donkey Kong Jr. sometimes interferes by flipping switches or throwing mushrooms to shrink Mario. The puzzles require precise timing and understanding of the game's physics.
In addition to the puzzle levels, each world has battles with Donkey Kong. These battles involve Mario reaching Pauline while avoiding falling debris and throwing objects back at Donkey Kong. After defeating a Donkey Kong boss level, there's a short cutscene of Mario chasing Donkey Kong, demonstrating a special move. The player also earns extra lives based on their remaining time in the previous levels.
Each stage has a time limit, and high scores are recorded. The Stage Clear screen shows if the player achieved a new record, and the high scores can be viewed by pressing Start or Select.
In the final Tower stage, each level involves chasing Donkey Kong and Donkey Kong Jr. to the top, avoiding their attacks, trapping Junior in a cage, and defeating a giant Donkey Kong in the final battle.